Autonomous vehicles, such as vehicles that do not require a human driver, can be used to aid in the transport of passengers or items from one location to another. Such vehicles may operate in a fully autonomous mode where passengers may provide some initial input, such as a destination, and the vehicle maneuvers itself to that destination.
Human drivers can use their vehicle's horns to signal different types of information to other persons, including drivers, pedestrians, or bicyclists. In some situations, these communications can include notifying other persons that the driver needs to take some action so that the driver can proceed, such as where the other person is stopped in the roadway, at an intersection, etc. and the driver's vehicle cannot safely proceed until the other person, and in some cases his or her vehicle or bicycle moves.